FIT TOLERANCES FOR PARALLEL / TAPER KEY - KEYSEAT ASSEMBLIES

ANSI B17.1 standard identifies two classes of stock for parallel keys. One is a close, plus toleranced key stock and the other is a broad, negative toleranced bar stock.
Each is combined with appropriate keyseat tolerances to make assemblies. Based on the use of two types of stock, two classes of fit are given.
Class 1 is a clearance or metal-to-metal side fit obtained by using bar stock keys and keyseat tolerances. This is a relatively free fit and applies only to parallel keys.
Class 2 is a side fit, with possible interference or clearance, obtained by using key stock and keyseat tolerances as given in this page. This is a relatively tight fit.

Fit Tolerances for Parallel & Taper Keys:

INPUT PARAMETERS

Key Type

Parallel KeyTaper Key

Fit Type

Class 1Class 2

Key Cross Section

SquareRectangular

Nominal Key Size Width [over - to (incl.)]

Please Wait...

RESULTS

Parameter

Value

Key Type

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Fit Type

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Key Cross Section

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Key Width [over - to (incl.)]

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inch

SIDE FIT

Key Width Upper Deviation

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inch

Key Width Lower Deviation

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Keyseat Width Upper Deviation

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Keyseat Width Lower Deviation

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Maximum Clearance

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Minimum Clearance

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TOP AND BOTTOM FIT

Key Depth Upper Deviation

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inch

Key Depth Lower Deviation

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Shaft Keyseat Depth Upper Deviation

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Shaft Keyseat Depth Lower Deviation

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Hub Keyseat Depth Upper Deviation

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Hub Keyseat Depth Lower Deviation

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Maximum Clearance

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Minimum Clearance

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Definitions:

Keyseat: An axially located rectangular groove in a shaft or hub. Hub keyseat has been sometimes referred to as a keyway

Sunk Key: A standard form of key with rectangular or square cross-section in which the key fits into the keyseats on the shaft and the hub.